Merge pull request #1788 from riscv-software-src/support-larger-addresses

Lift restriction on physical-address size

Author: aswaterman

riscv/cfg.cc

@@ -18,13 +18,15 @@ bool mem_cfg_t::check_if_supported(reg_t base, reg_t size)
   // the regions in the first place, but we have them here to make sure that
   // we can't end up describing memory regions that don't make sense. They
   // ask that the page size is a multiple of the minimum page size, that the
-  // page is aligned to the minimum page size, that the page is non-empty and
-  // that the top address is still representable in a reg_t.
+  // page is aligned to the minimum page size, that the page is non-empty,
+  // that the size doesn't overflow size_t, and that the top address is still
+  // representable in a reg_t.
   //
   // Note: (base + size == 0) part of the assertion is to handle cases like
   //   { base = 0xffff_ffff_ffff_f000, size: 0x1000 }
   return (size % PGSIZE == 0) &&
          (base % PGSIZE == 0) &&
+         (size_t(size) == size) &&
          (size > 0) &&
          ((base + size > base) || (base + size == 0));
 }

riscv/mmu.h

@@ -19,7 +19,7 @@
 #define PGSHIFT 12
 const reg_t PGSIZE = 1 << PGSHIFT;
 const reg_t PGMASK = ~(PGSIZE-1);
-#define MAX_PADDR_BITS 56 // imposed by Sv39 / Sv48
+#define MAX_PADDR_BITS 64
 
 struct insn_fetch_t
 {

riscv/sim.cc

@@ -336,7 +336,8 @@ void sim_t::set_procs_debug(bool value)
 
 static bool paddr_ok(reg_t addr)
 {
-  return (addr >> MAX_PADDR_BITS) == 0;
+  static_assert(MAX_PADDR_BITS == 8 * sizeof(addr));
+  return true;
 }
 
 bool sim_t::mmio_load(reg_t paddr, size_t len, uint8_t* bytes)

spike_main/spike.cc

@@ -191,6 +191,31 @@ merge_overlapping_memory_regions(std::vector<mem_cfg_t> mems)
   return merged_mem;
 }
 
+static mem_cfg_t create_mem_region(unsigned long long base, unsigned long long size)
+{
+  // page-align base and size
+  auto base0 = base, size0 = size;
+  size += base0 % PGSIZE;
+  base -= base0 % PGSIZE;
+  if (size % PGSIZE != 0)
+    size += PGSIZE - size % PGSIZE;
+
+  if (size != size0) {
+    fprintf(stderr, "Warning: the memory at [0x%llX, 0x%llX] has been realigned\n"
+                    "to the %ld KiB page size: [0x%llX, 0x%llX]\n",
+            base0, base0 + size0 - 1, long(PGSIZE / 1024), base, base + size - 1);
+  }
+
+  if (!mem_cfg_t::check_if_supported(base, size)) {
+    fprintf(stderr, "Unsupported memory region "
+                    "{base = 0x%llX, size = 0x%llX} specified\n",
+            base, size);
+    exit(EXIT_FAILURE);
+  }
+
+  return mem_cfg_t(base, size);
+}
+
 static std::vector<mem_cfg_t> parse_mem_layout(const char* arg)
 {
   std::vector<mem_cfg_t> res;
@@ -200,9 +225,9 @@ static std::vector<mem_cfg_t> parse_mem_layout(const char* arg)
   auto mb = strtoull(arg, &p, 0);
   if (*p == 0) {
     reg_t size = reg_t(mb) << 20;
-    if (size != (size_t)size)
-      throw std::runtime_error("Size would overflow size_t");
-    res.push_back(mem_cfg_t(reg_t(DRAM_BASE), size));
+    if ((size >> 20) != mb)
+      throw std::runtime_error("Memory size too large");
+    res.push_back(create_mem_region(DRAM_BASE, size));
     return res;
   }
 
@@ -213,42 +238,7 @@ static std::vector<mem_cfg_t> parse_mem_layout(const char* arg)
       help();
     auto size = strtoull(p + 1, &p, 0);
 
-    // page-align base and size
-    auto base0 = base, size0 = size;
-    size += base0 % PGSIZE;
-    base -= base0 % PGSIZE;
-    if (size % PGSIZE != 0)
-      size += PGSIZE - size % PGSIZE;
-
-    if (size != size0) {
-      fprintf(stderr, "Warning: the memory at [0x%llX, 0x%llX] has been realigned\n"
-                      "to the %ld KiB page size: [0x%llX, 0x%llX]\n",
-              base0, base0 + size0 - 1, long(PGSIZE / 1024), base, base + size - 1);
-    }
-
-    if (!mem_cfg_t::check_if_supported(base, size)) {
-      fprintf(stderr, "Unsupported memory region "
-                      "{base = 0x%llX, size = 0x%llX} specified\n",
-              base, size);
-      exit(EXIT_FAILURE);
-    }
-
-    const unsigned long long max_allowed_pa = (1ull << MAX_PADDR_BITS) - 1ull;
-    assert(max_allowed_pa <= std::numeric_limits<reg_t>::max());
-    mem_cfg_t mem_region(base, size);
-    if (mem_region.get_inclusive_end() > max_allowed_pa) {
-      int bits_required = 64 - clz(mem_region.get_inclusive_end());
-      fprintf(stderr, "Unsupported memory region "
-                      "{base = 0x%" PRIX64 ", size = 0x%" PRIX64 "} specified,"
-                      " which requires %d bits of physical address\n"
-                      "    The largest accessible physical address "
-                      "is 0x%llX (defined by MAX_PADDR_BITS constant, which is %d)\n",
-              mem_region.get_base(), mem_region.get_size(), bits_required,
-              max_allowed_pa, MAX_PADDR_BITS);
-      exit(EXIT_FAILURE);
-    }
-
-    res.push_back(mem_region);
+    res.push_back(create_mem_region(base, size));
 
     if (!*p)
       break;